Bottom line, this was not really a "failure to fire," but rather the safety mechanism of the trigger working as designed.
The other thing to think about is that if you are not pulling straight back on the trigger, you are moving your point of aim and your accuracy will suffer. Sometimes not enough to notice, but other times it can be the difference between winning and placing in a match, or perhaps when hunting, the difference between a "Dead Right There" shot instead of a wounding shot that requires hours of tracking.